T. Miyake

QUADRUPOLE MOMENT OF THE PROTON DRIP-LINE NUCLIDE 13O

Abstract The quadrupole moment of the proton drip-line nuclide 13O(Iπ=3/2−,T=3/2,T1/2=8.6 ms) has been determined for the first time by detecting its β-NQR signal following the production of polarized 13O through the projectile fragmentation process in the 16O + Be collision. The quadrupole moment has been determined to be |Q(13O)|=11.0±1.3 mb. The present result together with the quadrupole moment of its mirror partner 13B is compared with the theoretical values obtained by the shell model code, OXBASH, and by the Hartree-Fock calculation with its single proton separation energy taken into account.

Electromagnetic moments of short lived beta emitters F-21, Mg-23, Si-27 and Ca-39

The β-NMR spectra of 21F, 23Mg, 27Si and 39Ca which were produced in heavy ion collisions and implanted in various crystals have been observed. The magnetic moments of 21F and 27Si were determined to be |μ(21F)| = 3.9194 ± 0.0012 μN and |μ(27Si)| = 0.8653 ± 0.0003 μN, respectively. The electric quadrupole coupling constants were determined for the first time to be |eqQ(21F in MgF2)/h|= 9.94 ± 0.09 MHz, |eqQ(23Mg in MgF2)/h|= 1.96 ± 0.06 MHz, |eqQ(27Si in Al2O3)/h|= 1.90 ± 0.12 MHz, |eqQ(39Ca in CaCO3)/h|= 0.60 ± 0.04 MHz. From the present eqQ/h, the Q moments were deduced as |Q(21F)|= 110 ± 22 mb, |Q(23Mg)|= 114 ± 3 mb, |Q(27Si)|= 60 ± 13 mb and |Q(39Ca)|= 36± 7 mb. The present data were compared with the theoretical values obtained by the OXBASH shell model code.

A Possible Nuclear Spin Dewar. Hyperfine Interactions of Short-Lived β Emitter 8Li and 12B in TiO2

It was confirmed by detecting the β-NMR of 12B (Iπ=1+, T1/2=20.2 ms) in a TiO2 (rutile) crystal that the nuclear spin polarization of 12B was totally maintained in the crystal as produced through a nuclear reaction before implantation. Two locations, site 1 and site 2, were found with the relative populations 9 and 1, respectively, and the electric field gradients (EFGs) at those sites were obtained to be q(site 1)=+(37.1±0.5)1015 V/cm2, η(site 1)<0.03, q(site 2)=+(185±5)1015 V/cm2 and η(site 2)=0.62±0.02. We also found that about 30% of the initial polarization of 8Li (Iπ=2+, T1/2=838 ms) was maintained in the crystal. Since the polarizations of other β emitting nuclei, 12,16N, 13,19O, and 41Sc were also totally maintained in the crystal, the crystal can be a “Spin Dewar” in which many short-lived nuclides can be implanted with their polarizations totally maintained during their lifetimes for the studies not only on the electronic structure of impurities in it but also on the nuclear properties.

Electromagnetic moments of the β-emitting nucleus 19O

Abstract The nuclear magnetic-dipole moment μ and electric-quadrupole moment Q of the short-lived β -emitting nucleus 19 O (I π =5/2 + ,T 1/2 =27 s ) have been determined by detecting its β -NMR in CaO and TiO 2 crystals to be |μ|=(1.53195±0.00007) μ N and | Q |=(3.7±0.4) mb, respectively. Slight deviations of both values from the shell model predictions given by Hartree-Fock calculations demand further experimental and theoretical studies.

Hyperfine Interactions of 12B in CaB6

The hyperfine interactions of short-lived β-emitter 12B implanted into a CaB6 crystal have been studied by means of the β-NMR technique. An electric quadrupole splitting has been observed at room temperature from which an electric field gradient of q=−(1.34±0.05)×1021 V/m2 was determined. From the present result, it was found that the 12B nuclei are mainly implanted in the substitutional boron site.

Spin polarization of 23Mg in 24Mg+Au, Cu, and Al collisions at 91 A MeV

Spin polarization of beta‐emitting fragment 23Mg(Iπ=3/2+, T1/2=11.3 s) produced through the projectile fragmentation process in 24Mg+Au, Cu, and Al collisions has been observed at 91 AMeV. General trend in the observed momentum dependence of polarization is reproduced well qualitatively by a simple fragmentation model based on the participant‐spectator picture, for heavy and light targets. However the polarization behavior differs from this model in terms of zero crossing momentum, which become prominent in the case of Cu target, where the polarization is not monotone function of the fragment momentum.

Nuclear Spin Alignment of 12,13B Produced in Heavy Ion Collisions

The nuclear spin alignments of the β-emitting fragments 12B(Iπ=1+, T1/2=20.2 ms) and 13B(Iπ=3/2−, T1/2=17.4 ms) produced in the 100A-MeV 13C, 15N + 9Be collisions respectively have been observed for the first time detecting asymmetric β-ray emission from these nuclei. By means of the spin manipulation technique based on the hyperfine interaction of B isotopes in TiO2, both the polarization P and the alignment A were determined reliably. The obtained P and A were significantly smaller than the expectation from the kinematical model. From the fact that the quenching factors for P and A are almost the same, there may be some depolarization mechanism in the collision process itself.

Hyperfine Interactions of N Isotopes in TiO2 and Quadrupole Moment of 16N

Hyperfine interactions of 12,14N in BN(hexagonal) crystal were studied by detecting β-NQR(12N) and FT-NMR(14N). A β-NMR of 16N (Iπ=2−,T1/2=7.13 s) in MgO crystal was detected to determine the magnetic moment of 16N to be |μ(16N:2−)|=(1.986±0.001)μN. Also, the β-NQR of 12,16N in TiO2 crystal were detected to determine |Q(16N:2−)|=(17.9±1.7) mb. An abnormally small effective charge for neutrons is required to account for |Q(16N:2−)|.

Hyperfine interactions of 19O in TiO2 and quadrupole moments of 13,19O

The electric quadrupole interaction of 19O(Iπ=(5/2)+, T1/2=27.0 s) in TiO2 single crystal was studied in detail by means of the β-NQR to determine the electric quadrupole moments Q of short-lived β-emitting nuclei 19O and 13O(Iπ=(3/2)-, T1/2=8.6 ms). Two implantation sites were found for the implanted O nucleus and the quadrupole coupling constants of 19O at these sites were determined. We observed FT-NMR of the enriched stable isotope 17O in TiO2 and obtained the electric field gradient (EFG) at the oxygen substitutional site. With this knowledge, we have determined Q(13O)=11.0 ± 1.3 mb and Q(19O)=3.7 ± 0.4 mb. The present results are compared with the theoretical values calculated by the shell model code, OXBASH and by the Hartree–Fock calculation with the realistic potential.

Nuclear Structure Study through Nuclear Moments of Mirror Pairs

β‐NMR spectra have been observed for 33Cl, 23Al and 23Ne. As a result, the magnetic moment of 33Cl was determined as |μ(33Cl)| = 0.7549(3) μN. Combined with the known magnetic moment of 33S and the ft‐value of the 33Cl β decay, the orbital angular momenta and the intrinsic spins for proton and neutron groups, are deduced separately as 〈lp〉 = 1.3, 〈n〉 = 0.3, 〈Sp〉 = −0.12 and 〈Sn〉 = −0.02. The magnetic moment of 23Al, and that of 23Ne were determined as |μ(23Al)| = 3.89(22) μN and |μ(23Ne)| = 1.0817(9) μN, respectively. As a result, the orbital angular momentum 〈lz〉 and the intrinsic spin 〈Sz〉 were deduced to be 2.09(29) and 0.41(29), respectively. Combined with the ft‐value of the β transition from the ground state of 23Al to the excited state of 23Mg, proton and neutron contributions are separated. The obtained expectation values 〈lp〉, 〈ln〉, 〈Sp〉 and 〈Sn〉 are compared with the shell model predictions.